Low toxicity oil composition and use thereof in drilling fluids

Abstract

This invention relates to a base oil composition suitable for use in drilling fluids, the composition comprising an oil component with an aromatic hydrocarbon content of less than 10% w/w and a polar activator which is an ether alcohol or a mixture of ether alcohols. The polar activators used herein mitigates the problems of toxicity, shearing, stability and gelation in drilling fluids containing conventional base oils.

We claim: 
     
       1. A base oil composition suitable for use in organophilic clay-containing drilling fluids, said composition consisting essentially of: an oil component with an aromatic hydrocarbon content of less than 10% w/w; and from 1-5% of a polar activator which is an aliphatic or aromatic ether alcohol or is a mixture of ether alcohols selected from one or more of butoxypropanol, isobutoxypropanol, phenoxypropanol and phenoxypropoxy propanol. 
     
     
       2. A base oil composition according to claim 1 wherein the polar activator is a mixture of an aromatic ether alcohol and an aliphatic ether alcohol, the latter being present in the mixture in an amount from 20-50% w/w of the total mixture. 
     
     
       3. A drilling fluid consisting essentially of: one or more organophilic clays, and a base oil composition, said base oil composition consisting essentially of: an oil component with an aromatic hydrocarbon content of less than 10% w/w and from 1-5% w/w of a polar activator which is an aliphatic or aromatic ether alcohol or is a mixture of ether alcohols selected from one or more of butoxypropanol, isobutoxypropanol, phenoxypropanol and phenoxypropoxy propanol. 
     
     
       4. A drilling fluid according to claim 3 wherein said fluid is prepared by initially mixing the polar activator and one quarter of the oil component of the base oil composition with the clay, allowing the mixture to swell and gel, thereafter adding the remaining three quarters of the oil component to the swollen gel an finally shearing the total mixture to form the drilling fluid. 
     
     
       5. A drilling fluid as claimed in claim 3 wherein the polar activator is a mixture of an aromatic ether alcohol and an aliphatic ether alcohol, the latter being present in the mixture in an amount from 20-50% w/w of the total mixture. 
     
     
       6. A drilling fluid as claimed in claim 3 wherein the drilling fluid further contains one or more of water, halide salts of sodium or calcium, surfactants, emulsifiers, and weighting materials. 
     
     
       7. A drilling fluid as claimed in claim 6 wherein said fluid is prepared by initially mixing the polar activator and one quarter of the oil component of the base oil composition with the clay, allowing the mixture to swell and gel, thereafter adding the remaining three quarters of the oil component to the swollen gel and finally shearing the total mixture to form the drilling fluid.